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29 Cards in this Set
- Front
- Back
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What is potable water? |
It is another word for drinking water. |
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What are water mains? |
Layed by plumbers employed by water authority. Water authority plumber will do the tapping of the mains. |
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What is trunk water? |
It is water carried in bulk over long distances. |
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How is water mains system run through a town? |
Run through a town by a grid system. |
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Why is a grid system used? |
Provides a ring circuit and each section can be isolated in event of a burst main without need to isolate the full town. |
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What are water mains made from? |
Made from PVC, asbestos cement or cast iron. |
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What is the potential problem of using cast iron water mains? |
It is susceptible to deterioration in corrosive soils. |
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How is cast iron mains water pipe tapped? |
A special machine is designed to cut it to large diameter cast iron pipe while the water is still in the pipe and under pressure. |
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How far should a water mains be below the road? |
900mm below the road. |
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How far should water mains be below anywhere else? |
600mm |
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Why are water mains buried so far down? |
To prevent damage owing to settlement or frost. |
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Name section of pipework which lies between the water mains and local authority stop valve? |
Communication pipe |
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Name section of pipework located from stop valve to the house? |
Service pipe. |
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What is a gooseneck bend and where is it fitted? |
Gooseneck bend is used to allow for groups do movement and it is fitted into the communication pipe. |
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What depth is the service pipe below ground? |
600mm |
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What is applied around the service pipe at the point of entry to the house? |
Should be sleeved with a suitable duct. |
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What is done to prevent the entry of vermin to the house? |
Both ends of sleeve is sealed with mastic. |
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What is mains pipe called when it enters the house? |
Rising main |
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What is fitted to rising main at point of entry? |
Stop valve is fitted at point of entry to control the flow of water. |
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Explain directly stem of cold water supply? |
Mains supply capable of delivering adequate quantities of water at good pressure. |
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List 3 advantages of a direct system? |
Small cistern, cheaper to install and drinking water. |
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List 3 disadvantages of a direct system? |
Danger of back siphonage, danger of water hammer and pressure losses. |
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List 3 advantages of indirect system? |
Less back siphonage, less water hammer and adequate storage of cold water. |
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List 3 disadvantages of indirect system? |
More expensive, larger cistern, less drinking water. |
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What is the definition of back siphonage? |
The back flow of water by siphonic action from an appliance or storage cistern into the supply pipe leading to contamination. |
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What is the purpose of fitting a double check valve? |
To prevent occurance of back siphonage. |
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What is the purpose of fitting a drain valve? |
To allow pipework to be drained. |
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What actually capacity storage cistern should a 3 bedroom house or less have? |
212 litres. |
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What actually capacity storage cistern should a 4 bedroom or larger house have? |
340 litres. |
